Method and apparatus of forming ESD protection device

ABSTRACT

The present disclosure provides a semiconductor device having a transistor. The transistor includes a source region, a drain region, and a channel region that are formed in a semiconductor substrate. The channel region is disposed between the source and drain regions. The transistor includes a first gate that is disposed over the channel region. The transistor includes a plurality of second gates that are disposed over the drain region.

PRIORITY DATA

The present application is a divisional patent application of U.S.patent application Ser. No. 12/719,720, filed on Mar. 8, 2010, entitled“Method and Apparatus of Forming ESD Protection Device”, the disclosureof which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to a method of fabricating asemiconductor device, and more particularly, to a method of forming anelectrostatic discharge (ESD) protection device.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. These circuits may be sensitiveto electrostatic discharge (ESD) currents. Thus, ESD protection devicesare utilized to prevent and reduce damages to an IC caused by ESDcurrents. Traditionally, an ESD protection device utilizes asilicide-blocking layer to prevent a silicide from forming on a drainregion of the ESD device, thereby suppressing an ESD discharging currentand preventing non-uniform turn-on issues in the ESD protection device.However, implementing the silicide-blocking layer increases fabricationcosts and may require a larger chip area.

Therefore, while existing methods of fabricating ESD protection deviceshave been generally adequate for their intended purposes, they have notbeen entirely satisfactory in every aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a flowchart illustrating a method of forming an ESD protectiondevice according to various aspects of the present disclosure;

FIGS. 2-8 are diagrammatic fragmentary cross-sectional side views of theESD protection device at various stages of fabrication in accordancewith an embodiment of the method of FIG. 1;

FIG. 9 is a diagrammatic fragmentary cross-sectional side view of theESD protection device at one stage of fabrication in accordance with analternative embodiment of the method of FIG. 1;

FIG. 10 is a diagrammatic fragmentary cross-sectional side view of theESD protection device at one stage of fabrication in accordance withanother alternative embodiment of the method of FIG. 1; and

FIG. 11 is a diagrammatic fragmentary cross-sectional side view of theESD protection device at one stage of fabrication in accordance with afurther alternative embodiment of the method of FIG. 1.

SUMMARY

One of the broader forms of the present disclosure involves asemiconductor device that includes a transistor. The transistorincludes, a source region, a drain region, and a channel region that isdisposed between the source and drain regions; a first gate disposedover the channel region; and a plurality of second gates disposed overthe drain region.

Another of the broader forms of the present disclosure involves asemiconductor device that includes a transistor. The transistorincludes, a source region, a drain region, and a channel region that isdisposed between the source and drain regions; a functional gatedisposed over the channel region, the functional gate having a firstgate length; and a dummy gate disposed over the drain region, the dummygate having a second gate length that is smaller than the first gatelength.

Still another of the broader forms of the present disclosure involves amethod of fabricating a semiconductor device. The method includes,providing a substrate; forming a first gate and a plurality of secondgates over the substrate; and forming a source region and a drain regionin the substrate, the source and drain regions being separated by a gapthat defines a channel region; wherein the forming the source and drainregions is carried out in a manner so that the first gate is disposedover the channel region, and the plurality of second gates are disposedover the drain region.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of variousembodiments. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

FIG. 1 is a flowchart of a method 11 for fabricating a semiconductordevice. The method 11 begins with block 13 in which a substrate isprovided. The method 11 continues with block 15 in which a first gateand a plurality of second gates are formed over the substrate. Themethod 11 continues with block 17 in which a source region and a drainregion are formed in the substrate. The source and drain regions areseparated by a gap that defines the channel region. The first gate isdisposed over the channel region. The plurality of second gates aredisposed over the drain region.

FIGS. 2-8 are diagrammatic fragmentary cross-sectional side views of oneembodiment of an ESD protection device 40A at various stages offabrication in accordance with the method 11 of FIG. 1. FIG. 9 is adiagrammatic fragmentary cross-sectional side view of another embodimentof an ESD protection device 40B at a stage of fabrication in accordancewith the method 11 of FIG. 1. FIG. 10 is a diagrammatic fragmentarycross-sectional side view of still another embodiment of an ESDprotection device 40C at a stage of fabrication in accordance with themethod 11 of FIG. 1. FIG. 11 is a diagrammatic fragmentarycross-sectional side view of yet another embodiment of an ESD protectiondevice 40D at a stage of fabrication in accordance with the method 11 ofFIG. 1. It is understood that FIGS. 2-11 have been simplified for abetter understanding of the inventive concepts of the presentdisclosure. Accordingly, it should be noted that additional processesmay be provided before, during, and after the method 11 of FIG. 1, andthat some other processes may only be briefly described herein.

Referring to FIG. 2, the ESD protection device 40A is an N-typetransistor with a P-type substrate 45 that is doped with a P-type dopantsuch as boron. A P-well 47 is formed in the substrate 45. In anotherembodiment, the ESD protection device 40A may be a P-type transistorwith an N-type substrate that is doped with an N-type dopant such asarsenic or phosphorous.

Referring back to FIG. 2, isolation structures 50 and 51 are formed inthe substrate. In an embodiment, the isolation structures 50 and 51 areshallow trench isolation (STI) structures that include a dielectricmaterial, which may be silicon oxide or silicon nitride. The P-well 47is disposed in between the isolation structures 50 and 51.

Gate structures 70-73 are then formed over the substrate 45. The gatestructures 71-73 are dummy gates for reasons that will be discussedbelow. It is understood that three of these dummy gate structures 71-73are illustrated in FIG. 2 for purposes of facilitating ensuingdiscussions, and that other numbers of dummy gate structures may beformed in alternative embodiments.

The gate structures 70-73 include respective gate dielectric layers80-83. In an embodiment, the gate dielectric layers 80-83 includesilicon oxide. In another embodiment, the gate dielectric layers 80-83include a high-k dielectric material. A high-k dielectric material is amaterial having a dielectric constant that is greater than a dielectricconstant of SiO₂, which is approximately 4. For example, the high-kdielectric material may include hafnium oxide (HfO₂), which has adielectric constant that is in a range from approximately 18 toapproximately 40. Alternatively, the high-k material may include one ofZrO₂, Y₂O₃, La₂O₅, Gd₂O₅, TiO₂, Ta₂O₅, HfErO, HfLaO, HfYO, HfGdO, HfAlO,HfZrO, HfTiO, HfTaO, SrTiO, or combinations thereof.

The gate structures 70-73 also include respective gate electrode layers90-93 that are respectively disposed over the gate dielectric layers80-83. The gate electrode layers 90-93 include polysilicon. The gatestructures 70-73 further include respective hard mask layers 100-103that are respectively disposed over the gate electrode layers 90-93. Thehard masks 100-103 include a dielectric material, such as silicon oxideor silicon nitride. Although not illustrated herein, the hard masklayers 100-103 were formed by patterning a hard mask material with apatterned photoresist layer. The hard mask layers 100-103 were then usedto pattern the gate electrode layers 90-93 and the gate dielectriclayers 80-83 therebelow so as to form the gate structures 70-73.

The gate structures 70-73 have respective gate lengths 110-113. The gatelength 110 is in a range from approximately 300 nanometers (nm) toapproximately 500 nm. The gate lengths 111-113 are in a range fromapproximately 20 nm to approximately 40 nm. In the embodiment shown inFIG. 2, the gate lengths 111-113 are each equal to approximately 30 nm,and the gate length 110 is equal to approximately 300 nm. Distances (orgaps) 115, 116, 117 separate the gate structures 70-71, 71-72, and72-73, respectively. The distances 115-117 are equal to approximately 70nm. In other words, a pitch—defined as the length of a gate structureand the distance separating adjacent gate structures—of the gatestructures 70-73 is equal to approximately 100 nm.

After the gate structures 70-73 are formed, a lightly doped sourceregion 120 and lightly doped drain regions 121-127 are formed in theP-well 47 through an ion implantation process 130. Specifically, thelightly doped source region 120 and the lightly doped drain region 121are formed on either side of the gate structure 70, the lightly dopeddrain regions 122 and 123 are formed on either side of the gatestructure 71, the lightly doped drain regions 124 and 125 are formed oneither side of the gate structure 72, and the lightly doped drainregions 126 and 127 are formed on either side of the gate structure 73.The hard masks 100-103 protect portions of their respective gatestructures 70-73 therebelow during the ion implantation process 130. Agap between the lightly doped source region 120 and the lightly dopeddrain region 121 defines a channel region 135, where electrical currentwill flow when the ESD protection device 40A is turned on.

The ion implantation process 130 in FIG. 2 uses an N-type dopant such asarsenic or phosphorous to dope the regions 120-127. In an alternativeembodiment, the ion implantation process 130 may use a P-type dopantsuch as boron. The ion implantation process 130 also has a slight tiltangle and uses a relatively high implantation energy. In an embodiment,the tilt angle is in a range from approximately 7 degrees toapproximately 10 degrees, and the implantation energy is in a range fromapproximately 7 kilo-electro volts (KeV) to approximately 15 KeV. Theslight tilt angle and the high implantation energy leads to lateraldiffusion of the regions 120-127. As discussed above, the gatestructures 71-73 have respective gate lengths 111-113 that are equal toapproximately 30 nm in the present embodiment. Due in part to therelatively short gate lengths 111-113 and also to the lateral diffusionof the regions lightly doped drain regions 121-127, the lightly dopeddrain regions 121-127 merge together, which is also referred to as a“punch through” effect. As such, the lightly doped drain regions 121-127form a single lightly doped drain region 133 that provides a continuousconductive path for the flow of electrical currents.

Referring now to FIG. 3, gate spacers 140 and 141 are formed onsidewalls of the gate structure 70, gate spacers 142 and 143 are formedon sidewalls of the gate structure 71, gate spacers 144 and 145 areformed on sidewalls of the gate structure 72, and gate spacers 146 and147 are formed on sidewalls of the gate structure 73. The gate spacers140-147 are formed using a deposition process and an etching process(for example, an anisotropic etching process) known in the art. The gatespacers 140-147 include a suitable dielectric material such as siliconnitride, silicon oxide, silicon carbide, silicon oxy-nitride, orcombinations thereof. The gate spacers 140-141, 142-143, 144-145, and146-147 may be considered parts of the gate structures 70-73,respectively.

The spacers 140-147 each have a spacer thickness 150 that is greaterthan or equal to one half of each of the distances 115-117. For example,in the present embodiment, the distances 115-117 are equal toapproximately 70 nm. Thus, the spacers 140-147 have thicknesses 150 thatis greater than or equal to approximately 35 nm. As such, the spacers141 and 142 merge together, the spacers 143 and 144 merge together, andthe spacers 145 and 146 merge together.

After the spacers 140-147 are formed, an ion implantation process 160 isperformed on the ESD device 40A to form a heavily doped source region170 and a heavily doped drain region 171. The heavily doped sourceregion 170 is disposed between the isolation structure 50 and the spacer140, and the heavily doped drain region 171 is disposed between theisolation structure 51 and the spacer 147. Since the dopants of theimplantation process 160 cannot penetrate through the gate structures70-73 and the spacers 140-147, the heavily doped source region 170 isself-aligned with the gate spacer 140 of the gate structure 70, and theheavily doped drain region 171 is self-aligned with the gate spacer 147of the gate structure 73. The ion implantation process 160 uses anN-type dopant to dope the regions 170 and 171. In an alternativeembodiment where the lightly doped drain region was doped with a P-typedopant, the ion implantation process uses a P-type dopant as well. Thehard masks 100-103 and the spacers 140-147 protect regions of the P-well47 therebelow during the implantation process 160, including the lightlydoped source region 120 and the lightly doped drain region 133.

Referring now to FIG. 4, a silicidation process is performed on exposedsurfaces of the heavily doped source region 170 and the heavily dopedrain region 171 to form self-aligned silicides (also referred to assalicides) 180 and 181. The silicides 180 and 181 are respectivelyaligned with the spacers 140 and 147 since the heavily doped sourceregion 170 and the heavily doped drain region 171 are respectivelyaligned with the spacers 140 and 147. The gate structures 70-73 and thespacers 140-147 serve as silicidation masks in the silicidation process,so that the surface of the lightly doped drain region 133 is notsilicided. It is undesirable to have silicides formed on the surfaces ofthe lightly doped drain region 133 because an ESD discharging currentwould have been crowded within the silicides, which may causenon-uniform turn-on problems for the ESD protection device 40A.

Traditional methods do not form the gate structures 71-73 and thespacers 142-147, nor the lightly doped drain region 133. Instead,traditional methods typically form a long heavily doped drain region inplace of the lightly doped drain region 133, and thereafter form asilicide-blocking layer, such as a resist-protection oxide (RPO) layer,to shield a portion of the surface of the long heavily doped drainregion. Silicide would then be formed on the exposed portion of thesurface of the heavily doped drain region.

However, there are several drawbacks associated with the traditionalmethods. First, forming a silicide-blocking layer requires an extraprocessing step and thus increases fabrication costs. Second, aresistivity of a heavily doped drain region is lower than a resistivityof a lightly doped drain region. As such, for any given unit length, therelatively long heavily doped drain region used by the traditionalmethods would have a relatively low drain resistance (also referred toas a ballast drain resistance), which is undesirable since a high drainresistance may be desired to limit the amount of current in the drainregion. Consequently, to achieve a higher ballast drain resistance, ESDprotection devices fabricated according to the traditional methods mayrequire a longer drain length to compensate for the low resistivity inthe drain. This increases fabrication costs and chip sizes. Third, thesilicide-blocking layer may need to be accurately defined to cover onlya desired portion of the surfaces of the heavily doped drain region.This places additional burdens on the photolithography tools used toform the silicide-blocking layer.

In comparison, the present embodiment offers many advantages, it beingunderstood that different embodiments may offer different advantages,and that no particular advantage is required for any one embodiment. Oneadvantage is that the gate structure 71-73 are formed in the samefabrication process as the gate structure 70, and the spacers 142-147are formed in the same fabrication process as the spacers 140-141, thusthe ESD protection device 40A fabricated according to the presentembodiment incurs no extra fabrication cost. In other words, forming thegate structures 71-73 is fully compatible with existing fabricationprocess flows. Another advantage is that by forming the lightly dopeddrain region 133 adjacent to the heavily doped drain region 171, theballast drain resistance is dominated by the relatively high resistanceof the lightly doped drain region 133. Therefore, the ESD protectiondevice 40A can achieve the same overall ballast drain resistance evenwith a shorter drain length. This results in smaller chip sizes and mayfurther reduce fabrication cost per chip. Yet another advantage is thatthe heavily doped drain regions 170 and 171 are aligned with the spacers140 and 147, respectively, thus the desired silicides 180 and 181 areself-aligned with the heavily doped drain regions 170 and 171,respectively. The gate structures 71-73 and the spacers 142-147 functionas a blocking layer to prevent the silicidation of the surface of thelightly doped region 133. As such, the gate structures 71-73 and thespacers 142-147 are capable of performing the intended functions of thesilicide-blocking layer of the traditional methods without placingburdens on the photolithography tool to achieve accurate alignment.Still another advantage of the present embodiment involves achemical-mechanical-polishing (CMP) process that is to be performedlater and will be discussed in more detail below.

Referring now to FIG. 5, the spacers 140-147 and the hard mask layers100-103 are removed and an inter-layer (or inter-level) dielectric (ILD)layer 200 is formed over the substrate 45, the isolation structures50-51, and the gate structures 70-73. The ILD layer 200 may be formed bychemical vapor deposition (CVD), high density plasma CVD, spin-oncoating, sputtering, or other suitable methods. In an embodiment, theILD layer 200 includes silicon oxide. In other embodiments, the ILDlayer 200 may include silicon oxy-nitride, silicon nitride, or a low-kmaterial. In another alternative embodiment, the spacers 140-147 areonly partially removed.

Referring to FIG. 6, a CMP process 210 is performed on the ILD layer 200to expose a top surface of the gate structures 70-73. Following the CMPprocess 210, the top surfaces of the gate structures 70-73 aresubstantially co-planar with the top surface of the ILD layer 200adjacent to the gate structures 70-73. Had the gate structures 71-73 notbeen formed, the CMP process 210 may suffer from a “CMP dishing effect”,in which the polishing may result in a surface of the ESD protectiondevice 40A that is not substantially even or flat. This is because therate of polishing varies depending on the type of material that is beingpolished and/or the density of patterns on the substrate. Thus, therating of polishing near the gate structure 70 may be different than therate of polishing elsewhere in the ESD protection device 40A. Here, byimplementing the gate structures 71-73, which all include similar typesof materials, the rating of polishing is more evenly distributedthroughout the ESD protection device 40A, and thus the CMP dishingeffect is substantially reduced.

Although not illustrated, one or more annealing processes are performedon the ESD protection device 40A to activate the source regions 120 and170 and the drain regions 133 and 171. These annealing processes may beperformed before or after the CMP process 210.

Referring now to FIG. 7, the gate structures 70-73 are removed, therebyforming trenches (or openings) 220-223 in place of the gate structures70-73, respectively. The gate structures 70-73 may be removed in a wetetching or a dry etching process known in the art, while the rest of thelayers of the ESD protection device 40A remain substantially un-etched,including the ILD layer 200. This is performed in accordance with a“high-k last” approach. In an alternative embodiment, the gatedielectric layers 80-83 include the high-k dielectric material (insteadof silicon oxide) as discussed above and are not removed. Thisalternative embodiment is performed in accordance with a “gate-last”approach and will be discussed in more detail further below.

Referring now to FIG. 8, high-k gate dielectric layers 230-233 areformed in the trenches 220-223, respectively. The high-k gate dielectriclayers 230-233 include the high-k dielectric material as discussedabove. Although not illustrated, it is understood that an interfaciallayer may be formed in the trenches 220-223 before the high-k gatedielectric layers 230-233 are formed.

Thereafter, gate electrodes 240-243 are respectively formed within thetrenches 220-223 and over the high-k gate dielectric layers 230-233. Thegate electrodes 240-243 may be formed by CVD, physical vapor deposition(PVD), or another suitable technique. The gate electrodes 240-243 eachinclude a work function metal portion and a fill metal portion. The workfunction metal portion of the gate electrode 240 is an N-type workfunction metal (N-metal), which may be Ti, Al, Ta, ZrSi₂, TaN, orcombinations thereof. The work function metal portion of the gateelectrodes 241-243 are a P-type work function metal (P-metal), which maybe Mo, Ru, Ir, Pt, PtSi, MoN, WNx, or combinations thereof. The workfunction metal portions of the gate electrodes 240-243 each have arespective range of work function values that are associated with thematerial composition of the work function metal gate electrodes. Thework function values can be used to tune a work function of the ESDprotection device 40A so that a desired threshold voltage V_(t) for eachof the gate structures 251-253 is achieved. For example, the workfunction values of the work function metal portions of the gateelectrodes 241-243 may be tuned in a manner to achieve a desired ballastresistance of the lightly doped drain region 133. A higher thresholdvoltage V_(t) for the gate structures 251-253 results in a higherballast drain resistance, and vice versa. In other words, the materialcomposition of the work function gate electrodes are correlated with theballast resistance of the lightly doped drain region 133. Fill metalportions of the gate electrodes 240-243 include one of tungsten (W),Aluminum (Al), copper (Cu), and combinations thereof, and respectivelyserve as the main conductive portions of the gate electrodes 240-243.

Gate structures 250-253 are formed by the high-k gate dielectric layers250-253 and the gate electrodes 240-243, respectively. The gatestructure 250 serves as a functional gate structure of the ESDprotection device 40A. The gate structures 251-253 serve as dummy gatestructures of the ESD protection device 40A in the sense that the gatestructures 251-253 are not used to turn on the ESD protection device40A.

FIG. 9 is a fragmentary diagrammatic cross-sectional side view of analternative embodiment of the ESD protection device 40B. The ESDprotection device 40B is similar to the ESD protection device 40Adiscussed above and illustrated in FIGS. 2-8. Thus, similar featureswill be labeled the same for the sake of simplicity and clarity. The EDprotection device 40B is fabricated using a “gate-last” approach. Underthe “gate-last” approach, the gate dielectric layers 80-83 include thehigh-k dielectric material and would not have been removed when the gateelectrode layers 90-93 were removed, thus the high-k gate dielectriclayers 230-233 (FIG. 8) need not be formed in this alternativeembodiment. After the removal of the gate electrode layers 90-93, gateelectrodes 260-263 are formed over the high-k dielectric layers 80-83,respectively. The gate electrodes 260-263 are similar to the gateelectrodes 240-243 (FIG. 8) described above. Thus, gate structures270-273 are formed by the high-k gate dielectric layers 80-83 and thegate electrodes 260-263, respectively. The gate structure 270 is afunctional gate structure of the ESD protection device 40B, and the gatestructures 271-273 serve as dummy gate structures. As such, thegate-last embodiment of the ESD protection device 40B illustrated inFIG. 9 has similar advantages as the high-k last embodiment describedabove with reference to FIGS. 2-8.

FIG. 10 is a fragmentary diagrammatic cross-sectional side view ofanother alternative embodiment of the ESD protection device 40C. In thisembodiment, the fabrication processes are substantially similar to thehigh-k last embodiment described above with reference to FIGS. 2-8.Thus, similar features will be labeled the same for the sake ofsimplicity and clarity. For the ESD protection device 40C, the distances115A, 116A, and 117A that respectively separate the gate structures250-251, 251-252, and 252-253 are each equal to approximately 100 nm,instead of 70 nm. Alternatively stated, the pitch of the gate structures250-253 is equal to approximately 130 nm instead of 100 nm. Due to thelonger pitch, the spacers 141-142, 143-144, and 145-146 (FIGS. 3-4, notillustrated herein) do not overlap, and consequently heavily doped drainregions 172-174 are formed by an ion implantation process similar to theion implantation process 160 in FIG. 3. Thus, the heavily doped drainregions 172-174 are formed at the same time that the heavily dopedsource region 170 and the heavily doped drain region 171 are formed.Thereafter, silicides 182-184 are respectively formed on the surfaces ofthe heavily doped drain regions 172-174, at the same time that thesilicides 180 and 181 are formed.

The embodiment shown in FIG. 10 also utilizes the high-k last approachemployed by the embodiment shown in FIGS. 2-8 but involves some tradeoffconsiderations between ballast drain resistance and fabricationconcerns. More specifically, the shorter pitch in the embodiment shownin FIGS. 2-8 may put constraints on the fabrication processes, includingthe photolithography processes used to accurately define the gatestructures 70-73 (FIGS. 2-6) having such a small pitch. In comparison,the longer pitch in the embodiment shown in FIG. 10 allows theseconstraints to be relaxed. Though the presence of the heavily dopeddrain regions 172-174 may reduce the ballast drain resistance, theoverall ballast drain resistance is still higher compared to ESDprotection devices formed by traditional processes, since the highlyresistive lightly doped drain regions 121-127 dominate the ballast drainresistance. Further, the distances 115A-117A may be used to tune theballast drain resistance. As the distances 115A-117A increase, thelength of the heavily doped drain regions 172-174 increase, and thelengths of the lightly doped drain regions 121-127 decrease. Thislessens the contribution of the resistance of the lightly doped drainregions 121-127 to the overall ballast drain resistance, and as suchreduces the overall ballast drain resistance. Conversely, as thedistances 115A-117A decrease, the overall ballast drain resistance wouldincrease. In other words, the distances 115A-117A—the spacing betweenthe dummy gate structures 251-253—are correlated with the overallballast drain resistance of the ESD protection device 40C.

FIG. 11 is a fragmentary diagrammatic cross-sectional side view of yetanother alternative embodiment of the ESD protection device 40D. In thisembodiment, the fabrication processes are substantially similar to thegate last embodiment described above with reference to FIG. 9. Thus,similar features will be labeled the same for the sake of simplicity andclarity. Also similar to the embodiment shown in FIG. 10, the distances115A, 116A, and 117A that respectively separate the gate structures270-271, 271-272, and 272-273 are each equal to approximately 100 nm,instead of 70 nm. Consequently, heavily doped drain regions 172-174 andsilicides 182-184 are formed as well. In other words, the embodimentshown in FIG. 11 is a combination of the embodiment shown in FIG. 9 andthe embodiment shown in FIG. 10. Thus, the embodiment shown in FIG. 11also involves a small trade-off between fabrication process requirementsversus ballast drain resistance.

It is understood for each of the embodiments shown above, additionalprocesses may be performed to complete the fabrication of the ESDprotection device 40. For example, these additional processes mayinclude deposition of passivation layers, formation of contacts, andformation of interconnect structures (e.g., lines and vias, metallayers, and interlayer dielectric that provide electricalinterconnection to the device including the formed metal gate). For thesake of simplicity, these additional processes are not described herein.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure. For example, the ESD protection device may not belimited to an NMOS device and can be extended to a PMOS device with asimilar structure and configuration except that all doping types may bereversed and dimensions are modified according to PMOS design. Further,the PMOS device may be disposed in a deep n-well pocket for isolatingthe device.

What is claimed is:
 1. A method of fabricating a semiconductor device,comprising: forming a first dummy gate and a plurality of second dummygates over a substrate; after the forming of the first dummy gate andthe plurality of second dummy gates, forming a source region, a drainregion, and a channel region in the substrate; after the forming of thesource region and the drain region, replacing the first dummy gate andthe second dummy gates with a first functional gate and a plurality ofsecond functional gates, respectively; wherein: the drain region isformed to be a continuous region and the plurality of the secondfunctional gates are formed directly above the drain region; nodielectric isolation structures are formed between the channel regionand the drain region; a portion of the first functional gate is formeddirectly above a portion of the drain region; and the channel region isformed directly below the first functional gate and between the sourceregion and the drain region.
 2. The method of claim 1, wherein theforming of the drain region comprises forming a plurality of lightlydoped drain regions and forming a plurality of heavily doped drainregions, the lightly doped drain regions being interleaved with theheavily doped drain regions.
 3. The method of claim 1, wherein theforming of the source region and the drain region are performed withoutusing a photoresist mask.
 4. The method of claim 1, wherein the formingof the first dummy gate and the plurality of second dummy gatescomprises: forming the first dummy gate having a first gate length; andforming the second dummy gates that each have a respective second gatelength that is smaller than the first gate length.
 5. The method ofclaim 4, wherein the forming of the first dummy gate and the pluralityof second dummy gates is performed such that: the first gate length isin a range from approximately 300 nanometers to approximately 500nanometers; the second gate lengths are each in a range fromapproximately 20 nanometers to approximately 40 nanometers; and each ofthe second dummy gates is spaced apart from adjacent second dummy gatesby approximately 70 nanometers.
 6. The method of claim 1, wherein theforming of the source region and the drain region comprises forming alightly doped source region and a lightly doped drain region, whereinthe lightly doped drain region is formed below the plurality of seconddummy gates; and further comprising: after the forming of the lightlydoped source region and the lightly doped drain region, forming spacerson sidewalls of the first dummy gate and the second dummy gates; afterthe forming of the spacers, forming a heavily doped source region and aheavily doped drain region in the substrate; and forming a silicidelayer over the heavily doped drain region.
 7. The method of claim 6,further comprising: forming a shallow trench isolation in the substrate,wherein the heavily doped drain is formed to be in direct contact withthe shallow trench isolation.
 8. The method of claim 6, wherein theforming of the heavily doped source region and the heavily doped drainregion is performed such that the lightly doped drain region is disposedentirely between the heavily doped source region and the heavily dopeddrain region.
 9. The method of claim 6, wherein the forming of thelightly doped source region and the lightly doped drain region areperformed using an ion implantation process in which the first dummygate and the second dummy gates serve as implantation masks.
 10. Themethod of claim 9, wherein the ion implantation process is performedwith a tilt angle.
 11. A method of fabricating a semiconductor device,comprising: forming a plurality of dielectric structures in a substrate;forming a functional gate and a plurality of dummy gates over thesubstrate and between two of the dielectric structures, the functionalgate having a first gate length, the dummy gates each having a secondgate length that is smaller than the first gate length, wherein thefunctional gate is formed to have a gate dielectric, a gate electrodedisposed over the gate dielectric, and gate spacers disposed onsidewalls of the gate dielectric and the gate electrode; and forming alightly doped drain region directly below an entire bottom surface ofthe dummy gate, wherein a portion of the lightly doped drain region isformed to extend laterally below the gate dielectric of the functionalgate; and forming a heavily doped drain region, wherein at least aportion of the heavily doped drain region is formed to border one of thedielectric structures.
 12. The method of claim 11, wherein: the formingof the functional gate comprises forming a metal gate electrode of afirst type as the gate electrode; and the forming of the plurality ofdummy gates comprises forming, for each of the dummy gates, apolysilicon gate electrode or a metal gate electrode of a second typethat is different from the first type.
 13. The method of claim 11,wherein the forming of the dummy gates comprises forming a metal gateelectrode for each of the dummy gates, and wherein the forming of thedrain region comprises forming a drain region having a resistance thatis correlated to a material composition of the metal gate electrode ofthe dummy gates.
 14. A method of fabricating a semiconductor device,comprising: forming a first high-k dielectric layer and a plurality ofsecond high-k dielectric layers over a substrate; forming a first dummyelectrode layer and a plurality of second dummy electrode layers overthe first high-k dielectric layer and the second high-k dielectriclayers, respectively; after the forming of the first dummy electrodelayer and the plurality of second dummy electrode layers, forming alightly doped source region and a lightly doped drain region in thesubstrate; after the forming of the lightly doped source region andlightly doped drain region, forming spacers on sidewalls of the firstdummy electrode layer and the second dummy electrode layers; after theforming of the spacers, forming a heavily doped source region and aheavily doped drain region in the substrate; after the forming of theheavily doped source region and heavily doped drain region, removing thefirst and second dummy electrode layers to form a first trench over thefirst high-k dielectric layer and a plurality of second trenches overthe second high-k dielectric layers, respectively; and forming a firstmetal gate electrode layer over the first high-k dielectric layer and aplurality of second metal gate electrode layers over the second high-kdielectric layers, respectively, the first metal gate electrode layerincluding material of a first type, and the second metal gate electrodelayer including material of a second type that is opposite from thefirst type.
 15. The method of claim 14, further including forming asilicide over the heavily doped drain region.
 16. The method of claim14, wherein the forming of the heavily doped source region and theheavily doped drain region is performed such that the lightly dopedsource region and the lightly doped drain region are disposed entirelybetween the heavily doped source region and the heavily doped drainregion.
 17. The method of claim 14, wherein the first metal gateelectrode layer is formed to have a first gate length, and the secondmetal gate electrode layers are formed to each have a respective secondgate length that is smaller than the first gate length.
 18. The methodof claim 17, wherein the first gate length is in a range fromapproximately 300 nanometers to approximately 500 nanometers; and thesecond gate lengths are each in a range from approximately 20 nanometersto approximately 40 nanometers.
 19. The method of claim 14, wherein theforming of the lightly doped source region and the lightly doped drainregion is performed using an ion implantation process in which the firstdummy electrode layer and the second dummy electrode layers serve asimplantation masks.
 20. The method of claim 19, wherein the ionimplantation process is performed with a tilt angle.